Randomized, multicenter, open-label, phase III study of the BTK inhibitor ibrutinib versus chlorambucil in patients 65 years or older with treatment-naive CLL/SLL (RESONATE-2, PCYC-1115-CA).

TPS7130 Background: There is an unmet need for safer and more effective therapies for CLL patients who are older/have comorbidites. Ibrutinib, a small molecule inhibitor of BTK, has demonstrated single-agent activity in CLL in the Ph 1b/2 study, PCYC-1102-CA. Treatment-naïve (TN) patients aged >= 65 yrs (n=31) experienced an estimated PFS and OS of 96% at 26 months; ORRs per iwCLL were: 10% CR, 58% PR, and 13% PR with lymphocytosis (Byrd, ASH 2012). AEs were generally Grade 1/2, most commonly diarrhea. Incidence of Grade 3/4 hematologic toxicities was low. These findings support a phase III study of ibrutinib in older patients with treatment-naïve CLL/SLL. Methods: The ongoing study is a randomized, multicenter, open label Ph 3 study comparing safety and efficacy of ibrutinib vs. chlorambucil in TN patients aged >= 65 yrs with CLL/SLL. Approximately 272 patients will be randomized in 1:1 ratio to receive either chlorambucil or ibrutinib, stratified for ECOG PS and Rai stage. Oral chlorambucil will be administered at 0.5 mg/kg on Days 1 and 15 of each 28-day cycle, for up to 12 cycles. Ibrutinib 420 mg q.d. will continue until PD or unacceptable toxicity. Key incl. criteria include age >= 65 yrs, active disease requiring treatment per iwCLL, measurable nodal disease by CT, ECOG performance status 0-2, and adequate organ function (ANC ≥1,000/μL, platelets ≥50,000/μL, creatinine clearance ≥30 mL/min). Key excl. criteria include Richter’s transformation, del(17p13.1) or previous treatment for CLL/SLL. The primary endpoint of the study is PFS, assessed by Independent Review Committee (IRC). Secondary endpoints include ORR, MRD-negative CRs, fatigue by FACIT-F, hematological improvement, safety, and tolerability. Subjects who relapse on PCYC-1115 will be enrolled on PCYC-1116 for long term follow up. Second line therapy is investigator choice; ibrutinib will be made available for patients who experience IRC-confirmed PD ≤12 months of completing chlorambucil therapy, if they meet the treatment criteria. Approximately 85 sites will enroll patients in North America, Europe, Israel, Australia/New Zealand and China. Enrollment began in Q1 2013. Clinical trial information: NCT01722487.